[llvm] [PGO] Sampled instrumentation in PGO to speed up instrumentation binary (PR #69535)

[David Li via llvm-commits]

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@@ -148,6 +150,16 @@ cl::opt<bool> SkipRetExitBlock(
     "skip-ret-exit-block", cl::init(true),
     cl::desc("Suppress counter promotion if exit blocks contain ret."));
 
+static cl::opt<bool>
+    SampledInstrument("sampled-instr", cl::ZeroOrMore, cl::init(false),
+                      cl::desc("Do PGO instrumentation sampling"));
+
+static cl::opt<unsigned> SampledInstrumentDuration(
+    "sampled-instr-duration",
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david-xl wrote:

The current sampling period is implicit to take advantage of  the wrapping behavior to reduce runtime overhead (and code size) -- we don't want to lose that. However I think the implementation can check if the bursty duration is not one, assert that sampling period is not set. Otherwise, generate the non bursty style sampling.

https://github.com/llvm/llvm-project/pull/69535